(Excerpt from The Star Principle by Richard Koch)
Subtracting benefits is important because it usually enables the new category to lower costs, and/or to substitute the new benefits without charging more, because of the saving on the benefits subtracted. Subtracting benefits is also useful to differentiate sharply the new category from the main market, and to make it clear that it is for a different kind of customer. Subtracting is sometimes the essence of the innovation.